Frequently Asked Questions
Our website lists the investigations that we can provide immediately using our Sonic laboratories. This list is regularly updated. However, there are many thousands of other genetic tests which are available in laboratories across Australia and worldwide.
We maintain an up-to-date listing of reliable accredited laboratories which provide these investigations, and can arrange for samples to be sent to one of these laboratories for a particular investigation.
Please contact Sonic Genetics on 1800 010 447 to discuss your particular request, and our staff will be able to provide you with the availability, cost, and turnaround time for this investigation.
Genetic testing for familial breast cancer raises a number of significant clinical, technical, and ethical challenges. At this stage, Sonic Genetics does not offer genetic testing for familial breast cancer. We recommend that patients requesting genetic testing for familial breast cancer be referred to a local familial cancer clinic to review these issues and decide what testing is feasible and appropriate.
Details of familial cancer clinics in Australia can be found here. There are also a few clinical geneticists in private practice who can provide appropriate advice and access to breast cancer gene testing.
The reason for our recommendation is as follows.
- Breast and ovarian cancers are frequently diagnosed in our community. A familial cluster of these cancers can be due to chance, common environmental factors, multiple shared genes between family members, or a single abnormal gene with a high risk of breast or ovarian cancer. At present, genetic testing can only reliably identify the last category i.e. an individual abnormal gene with a high risk of breast cancer. The BRCA1 and BRCA2 genes are examples of such genes. These genes account for only a small proportion of familial breast and ovarian cancer. A normal result from testing the BRCA1 and BRCA2 genes does not necessarily mean that a person is not at high risk of developing breast cancer; the person may still be at high risk of developing breast cancer because of the other risk factors listed above.
- The testing of genes which cause familial breast and ovarian cancer is relatively expensive (compared with many other medical tests), and should only be initiated when the chance of the test providing information, the potential utility of that information, and the cost are acceptable to the patient. The assessment of the chance of such a test being useful for a specific person is complex and may rely on the use of specialised clinical algorithms or sophisticated computer programs.
- Family history is an imperfect guide to the risk of a woman developing breast cancer, but it may be the best guide available as it includes common environmental factors, multiple shared genes between family members, and breast cancer due to a single abnormal gene inherited within the family. General practitioners, breast surgeons, medical oncologists, and familial cancer services are able to provide advice regarding breast cancer risk on the basis of a woman’s family history. Information and a risk-assessment tool are available from Cancer Australia.
- There is an important exception to this discussion. If a familial cancer gene has already been identified in the family, a genetic test to determine the presence or absence of this specific abnormality can provide accurate and useful information regarding cancer risk and prevention. However, such a test in an unaffected person raises significant ethical, social, and psychological issues, in addition to the anticipated medical issues. Such testing should only be arranged through an appropriately qualified genetic professional.
We constantly review our test list, the information available for doctors and patients, the resources we can provide to doctors and patients, and the price of genetic testing. This recommendation regarding genetic testing for familial breast and ovarian cancer may change in the future.
The gene responsible for cystic fibrosis is called CFTR. It is a relatively long gene, and it can be inactivated by any one of many different types of genetic error (or “mutation”). Over 1600 different mutations in the CFTR gene have been identified. However, some of these CFTR gene mutations are much more common than others. The most common mutation is called F508del (or deltaF508) and it occurs in approximately 75% of abnormal CFTR genes in Australians of European descent. At the other end of the scale, there are rare mutations in the CFTR gene that have been identified in only a few families worldwide. The analysis of mutations in the CFTR gene is further complicated by different mutations occurring at different frequencies in different ethnic groups.
It is feasible, but expensive, to examine the entire CFTR gene for all possible mutations. This comprehensive analysis of the CFTR gene is often unnecessary because certain mutations, such as deltaF508, are so common that it is cheaper and quicker to examine for these mutations first.
There are a number of different lists or “panels” of mutations that are examined by laboratories testing the CFTR gene. Some laboratories may test for just the deltaF508 mutation because it is by far the most common mutation in the CFTR gene. Other laboratories test for a number of different CFTR mutations. However, checking for rare mutations will result in only a small increase in the overall number of abnormal CFTR genes detected. Doubling the number of mutations examined does not double the number of abnormal genes detected.
The number of mutations examined is a major factor in determining the price of the investigation. The CFTR gene mutations that should be included in a cystic fibrosis screening test have been determined by national and international expert bodies, such as the Human Genetics Society of Australasia and the American College of Obstetrics and Gynaecology.
At Sonic Genetics, the 31 most common CFTR mutations are examined using a test called the Oligonucleotide Ligation Assay, or CF-OLA, which detects more than 88% of the mutations found in cystic fibrosis cases in people of European descent. The CF-OLA test is used by medical laboratories all over the world and is considered a ‘gold standard’ mutation screening test. It meets both national and international CF screening guidelines.
The CF-OLA test is frequently sufficient to answer the question asked by the patient or doctor. However, there will be rare situations in which more detailed analysis is warranted. For example if a family has a ‘rare’ CFTR gene mutation which is not covered by the CF-OLA panel, then more comprehensive testing will be needed. It is important that the laboratory is informed if there is such a family history so that we can advise about the suitability of this investigation. When the patient does not know the specific CFTR gene mutation in a family member, then the CF-OLA test is still a good initial test to eliminate the most common mutations.
Comprehensive analysis is much more expensive than testing for the common CFTR gene mutations, but these prices are falling. Sonic Genetics keeps this matter under review, and may change the CFTR gene tested offers in the future.